Rifle barrel



1966 A. J. GRANDY ETAL 3,228,298

RIFLE BARREL Filed April 20, 1960 2 Sheets-Sheet 1 Fig.

III/II I INVENTORS ANDREW J. GRANDY JOHN J. DONNELLY JR..

ATTORNEY Jan. 11, 1966 J. GRANDY ETAL RIFLE BARREL 2 Sheets-Sheet 2 Filed April 20 1960 INVENTORS ANDREW J. (BRANDY JOHN J. DONNELLY 04/. 1,

ATTORNEY United States Patent Filed Apr. 20, 1960, Ser. No. 23,582 Claims. (Cl. 8916) (Granted under Title 35, U.S. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to us of any royalty thereon.

This invention relates to the structure of pressure vessels, and has for its principal object the provision of an improved wall structure whereby the weight of such vessels may be greatly reduced without impairing their ability to withstand the pressures imposed upon them during their normal use.

Various attempts have been made to reduce the weight of vessels which are required to withstand high internal pressures. These attempts have largely involved the substitution of one material for another. For example, it has been proposed to substitute aluminum titanium or fiberglass for steel. The ability of such substitute materials to withstand pressures in the neighborhood of 10,000 pounds per square inch or more, however, has not proved altogether satisfactory.

In accordance with the present invention, this difliculty is minimized by making the vessel wall in the form of a metal liner which is prestressed in compression by a surrounding layer of fiberglass reinforced plastic, metal or the like as hereinafter explained. This metal liner (1) may have a smooth exterior (2) may be grooved, or (3) may have wires or other structural members between it and the surrounding layer. Depending on the stress to be withstood by the vessel, the wall may include a multiplicity of layers surrounding the liner. Where the vessel is a gun barrel, the wire or ridges in between the liner and the outer layer may be arranged to rifle the barrel automatically in response to the gas pressure incidentto the firing of the weapon.

The invention will be better understood from the following description when considered in connection with the accompanying drawings and its scope is indicated by the appended claims.

Referring to the drawings:

FIG. 1 is a fragmentary sectional view of a pressure vessel wall wherein the exterior surface of the metal liner is smooth,

FIG. 2 illustrates a modification wherein the outer surface of the metal liner is grooved, these grooves having a desired n'fling pitch in the case of a gun barrel,

FIG. 3 shows the intermediate layer as consisting of a plurality of wires which may be parallel with the axis of the vessel or at an angle with this axis.

FIG. 4 shows the wall as having rectangular members between the liner and outer fiberglass reinforced plastic,

FIG. 5 differs from FIGS. 3 and 4 in that it shows the wall as consisting of a plurality of intermediate layers,

FIG. 6 is a sectional view of a gun barrel showing the contour of the liner prior to firing of the gun,

FIG. 7 is a similar view illustrating how the liner is deformed to provide a rifiing which may be transient or permanent depending on the elastic limit of the liner, and

FIGS. 8 and 9 illustrate a modified type of gun barrel which is lighter than that of FIGS. 6 and 7.

The pressure vessel wall of FIG. 1 includes a liner 10 which may be sheet steel formed into the desired shape of the vessel. Surrounding the liner 10 is a layer of 3,228,298 Patented Jan. 11, 1966 fiberglass reinforced plastic 11. The layer 11 consists of glass roving and resin proportioned in the order of 70 percent of the glass roving to 30 percent of the resin. Since the modulas of elasticity of steel is around 30,000,000 pounds per square inch and that of the fiberglass reinforced layer is around 10,000,000 per square inch, it is necessary that the liner 10 be prestressed in compression by the layer 11 in order to fully utilize the strengths of the two materials.

This can be accomplished by various methods. One satisfactory method is to apply the plastic layer to the liner and stress this composite structure in compression while curing the plastic layer. Since the layer 11 is thermohardening, this leaves the liner prestressed in compression.

A satisfactory method of applying the layer 11 to the liner 10 is to draw the glass roving through powdered resin as it is wound on the liner at high speed and brushing a layer of resin on the outer surface of the composite structure. The layer 11 is then heated to polymerize its constituents after which it is cooled and the pressure is removed, leaving the liner pre-stressed in compression. The plastic layer is similarly applicable to the wall structures illustrated by FIGS. 2, 3 and 4.

In the structure of FIG. 2, a plurality of ridges or risers 12 are an integral part of the liner 10 and may be formed thereon by milling or other appropriate manipulation.

The structures of FIGS. 3 and 4 differ from that of FIG. 2 in that ridges 12 are replaced by wires 13 or rectangular structural members 14.

It has been found that a vessel having a wall of any of the above described types weighs only about three fourths as much as a solid'metal walled vessel capable of withstanding the same pressure. Obviously any desired number of additional layers 11' and 13' of metal and plastic may be added, as indicated by FIG. 5, if greater strength is desired.

FIGS. 6 and 7 illustrate how the wall of FIG. 2 may be utilized in a gun barrel. In these figures, the space between the lands or ridges 12 conform to the desired rifiing of the gun. FIG. 6 indicates the inner contour of the liner 10 prior to the firing of the gun and FIG. 7 indicates how this contour is deformed by the pressure generated by the firing of the gun. While this pressure is at the rear of the projectile, it is found that the rifiing effect proceeds along and somewhat in advance of the projectile and cooperates with a rotating band to spin the projectile.

In the static or unfired state, the interior of the liner 10 is essentially a smooth bore. Upon the application of sufiicient pressure, however, the rifiing appears in the form of the corrugations 15 of FIG. 7. Interference of the rotating band of the projectile with these corrugations imparts spin to the projectile.

The gun barrel illustrated by FIG. 8 differs from that of FIGS. 6 and 7 in that steel wires 16 are laid upon the liner or tube with the desired twist about the axis of the tube and fiberglass reinforced plastic laid over the tube and wires. This results in a barrel which is relatively light and is capable of imparting spin to the projectile. In a further modification, the wires 16 are laid in grooves 17, as indicated by FIG. 9, and thereafter given a coating of fiberglass reinforced plastic.

The above described wall structures have the advantage that (1) they eliminate or minimize the machining required to rifle gun tubes, (2) they are light as compared to presently available structures, and (3) they make possible the employment of rifiing in rifle tubes having wall thicknesses that would prohibit standard rifiing procedures.

We claim:

1. In a rifle barrel, the combination of an outer tube consisting of a fiberglass reinforced plastic, an inner metal flexible tube having a smooth bore and substantially coextensive in length with said outer tube, and a plurality of risers spaced apart extending between said tubes longitudinally thereof and having a longitudinal twist conforming to a desired rifling of said barrel, said outer tube exerting through said risers a force whereby said inner tube is prestressed in compression and the wall of said inner tube having a thickness such that said smooth bore is changed to a rifled bore by flexure upon the application of a predetermined gas pressure therein.

2. A rifle barrel according to claim 1 wherein said risers and said metal tube are a one-piece member.

3. A rifle barrel according to claim 1 wherein said risers are separate members.

4. A rifled barrel comprising an inner cylindrical tube, a plurality of wires secured to the outer surface of the inner tube, the wires following a generally spiral path thereon in spaced generally parallel relation to each other, an outer tube, said inner tube inserted inside said outer tube, the size of the outer tube such that the said spaced parallel Wires secured to the outer surface of the inner tube bear against the inner surface of the outer tube reinforcing thereby the wall portion of the inner tube covered by the wires, the wall portions of. the inner tube between the Wires yieldable so that if a projectile is fired through said barrel, the resulting pressure in the inner tube deforms the yieldable portions of the wall of the inner tube toward the inner surface of the outer tube while the reinforced wall portions of the inner tube beneath the spirally positioned wires do not deform and serve thereby as the rifling.

5. A rifled barrel comprising an inner cylindrical tube, a plurality of risers on the outer surface of the inner tube, the risers following a generally spiral path thereon in spaced generally parallel relation to each other, an 5 outer tube, said inner tube inserted inside said outer tube, the size of the outer tube such that the said spaced parallel risers on the outer surface of the inner tube bear against the inner surface of the outer tube reinforcing thereby the wall portion of the inner tube covered by the risers, the wall portions of the inner tube between the risers yieldable so that if a projectile is fired through said barrel, the resulting pressure in the inner tube deforms the yieldable portions of the wall of the inner tube toward the inner surface of the outer tube while the reinforced wall portions of the inner tube beneath the spirally positioned risers do not deform and serve thereby as the rifling.

References Cited by the Examiner UNITED STATES PATENTS 734,965 7/1903 Schinneller 8916 2,609,631 9/1952 Garand 8916 2,847,786 8/1958 Hartley et al. 89l6 X FOREIGN PATENTS 7,071 4/ 1894 Great Britain.

BENJAMIN A. BORCI-IELT, Primary Examiner.

SAMUEL FEINBERG, ARTHUR M. HORTON, SAM- UEL BOYD, Examiners.

FRED C. MATTERN, ]R., C. C. WELLS, W. E.

STEWART, Assistant Examiners. 

1. IN A RIFLE BARREL, THE COMBINATION OF AN OUTER TUBE CONSISTING OF A FIBERGLASS REINFORCED PLASTIC, AN INNER METAL FLEXIBLE TUBE HAVING A SMOOTH BORE AND SUBSTANTIALLY COEXTENSIVE IN LENGTH WITH SAID OUTER TUBE, SAID TUBES LONGITUDINALLY THEREOF AND HAVING A LONGITUDINAL TWIST CONFORMING TO A DESIRED RIFLING OF SAID BARREL, SAID OUTER TUBE EXERTING THOURGH SAID RISERS A FORCE WHEREBY SAID INNER TUBE IS PRESTRESSED IN COMPRESSION AND THE WALL OF SAID INNER TUBE HAVING A THICKNESS SUCH THAT SAID SMOOTH BORE IS CHANGED TO A RIFLED BORE BY FLEXURE UPON THE APPLICATION OF A PREDETERMINED GAS PRESSURE THEREIN. 